This invention relates to means for attaching a ceramic dome to an airframe.
Ceramic radomes appear to offer the best combination of low weight, high temperature strength, electromagnetic transmissibility, and thermal insulation, particularly for missiles encountering boundary layer temperatures over 800.degree. F. (425.degree. C.). The problem of attaching ceramic domes to metallic airframes arises from two fundamental differences in the characteristics of ceramics and metals. The first and probably most important characteristic is that of the coefficients of thermal expansion. Metals generally have higher coefficients of thermal expansion than ceramics. The second characteristic is that of thermal conductivity. Metals have relatively high thermal conductivity, while that of ceramics is relatively low.
Under conditions of rapid temperature increase at the external surfaces of a radome or nose cone, as occurs in flight due to aerodynamic heating effects, it is found that the radome mounting bracket of the metal airframe may become hotter than the ceramic radome because of the differing thermal conductivity characteristics. As a result of the higher thermal conductivity and expansion, the metal body expands radially to a greater degree and faster than the ceramic body. Direct attachment of the ceramic body to the metal body affords no allowance for differential expansion, and this produces a severe tensile stress in the ceramic wall resulting in fracture or complete failure of the ceramic body inasmuch as ceramics typically have relatively low tensile strengths. Slotting of the metal body to avoid circumferential stress permits leakage of high temperature air into the interior of the airframe, which could damage interior components.
There have been several approaches to attaching ceramic radomes to metal airframes; however, most approaches are either complex, difficult to assemble, or ineffective.
It is an object of the present invention to provide a radome assembly which overcomes the aforementioned disadvantages.
It is another object of the present invention to provide a method for attaching a ceramic radome to a metal airframe which overcomes the aforementioned disadvantages.
Other objects, aspects and advantages of the present invention will become apparent from the following detailed description of the invention, together with the appended claims and the accompanying drawing.